Recently light emitting diode (LED) based lighting solutions are gaining popularity over traditional light sources such as incandescent lamps, Fluorescent Lamp, Halogen lamps, and high intensity discharge (HID) lights. LED offers highly reliable and energy efficient lighting solutions. LED light output is controlled by forward current flowing through it, hence LED-based lighting solutions need current control electronic circuits. Cost, volume, weight and efficiency of electronics driver circuit's components play a major role in order to make LED lighting solutions successful for retrofit applications as well as new products developments.
The constant current sources for LEDs are derived using standard DC-DC converter topologies. These may include non-isolated DC-DC converters such as buck, boost, buck-boost, Sepic/cuk converters, or isolated topologies like fly back, forward converters etc. The control logic for these power supplies is modified in such a way to maintain constant LED current. This is achieved by sensing LED current and comparing it with a reference value. The list of these converters can be huge but all these solutions use free-wheeling diode(s) and a bulk capacitor in an output section. All these solutions suffer in terms of efficiency, cost, weight and volume because of the output filter capacitor and freewheeling diodes.
Some recent solution shows an optimized LED driver topology without an output bulk filter capacitor to reduce cost, weight and volume of LED drivers. Although this solution suffers in terms of efficiency, weight, cost and volume due to use of freewheeling diodes. Freewheeling diodes create switching and conduction losses which reduces efficiency and require bulkier heat-sinks for larger heat dissipation. In order to improve the efficiency and reduce heat-sink requirements, fast recovery and/or Schottky silicon carbide diodes are used; however this increases the cost of LED drivers.